Fukushima plant stabilised, Tepco claims

The crippled reactors at Japan's tsunami-hit nuclear power plant have reached stability, more than four months since the disaster.

The plant is now on track for a cold shutdown within six months, the government and plant operator said Tuesday (local time).

Workers have toiled in hot and harsh conditions to stabilise the Fukushima Dai-ichi plant since the March 11 earthquake and tsunami destroyed reactor cooling systems, triggering partial meltdowns of the reactors and making the disaster the world's worst nuclear crisis since Chernobyl.

The assessment of reactor stability was based on several milestones: temperatures at the bottom of reactor pressure vessels are no longer climbing, a makeshift system to process contaminated water works properly after initial problems and nitrogen injections are helping prevent more explosions.

Radiation around the plant has shown a "sufficient decrease" from peak levels measured soon after the disaster, according to the report released by the government and Tepco, the plant's operator.

The progress achieves Tepco's initial goals of its road map to bring the plant under control, the report said.

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"The accident has not been resolved, but we have been making progress steadily," trade and industry minister Banri Kaieda said. "We will continue our utmost effort so that we can bring this to an end as soon as possible."

The work now shifts into a second stage, when workers will aim to further cut radiation released into the air, soil and water. They expect a cold shutdown sometime in January.

A reactor reaches cold shutdown when the temperature at the bottom of the reactor pressure vessel drops below 100 degrees Celsius, and when the release of radioactive materials is "under control".

Tepco also said it will continue to improve conditions for workers by expanding temporary dormitories and onsite rest stations, as well as stronger controls over their radiation exposure.